The overall goal of this project is to validate promising diagnostic and prognostic assays for early stage breast cancer using large numbers of paraffin embedded tumor tissue specimens with associated clinical information and follow-up data. Stage TINO breast cancer tissues with 8 years of clinical follow-up information will be made available for the validation of diagnostic and prognostic assays. In studies designed by the NCI in collaboration with the Principal Investigator, breast cancer tissues will be analyzed using a variety of immunohistochemical assays, which may include, but are not limited to Estrogen Receptor, p53, erbB2 and PCNA. In addition, flow cytometric analyses of cell proliferation will be performed. The tumor tissue specimens will be shipped to other investigators or to the NCI for further analysis of these or other promising diagnostic and prognostic approaches. Clinical and experimental data will be supplied to the NCI for statistical analysis. This master agreement order will allow the validation of promising diagnostic and prognostic assays for early stage breast cancer in large numbers of well-characterized tumor tissues. Diagnostic and prognostic assays for early stage breast cancer that identify subgroups of patients who may benefit from more aggressive treatment should have an impact on breast cancer mortality.